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FORENSICS OF BLOOD SUNDAY ACADEMY 2011-12

This resource provides an overview of serology, blood typing, and blood spatter analysis in forensic investigations. Learn about the different components of blood, blood groups, blood testing methods, and the interpretation of blood spatter patterns. Engage in interactive activities to test your knowledge and understanding of blood forensics.

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FORENSICS OF BLOOD SUNDAY ACADEMY 2011-12

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  1. FORENSICS OF BLOODSUNDAY ACADEMY2011-12

  2. SEROLOGY Examples: • Blood • Saliva • Sweat • Etc. What is serology? Serology is the study of serums.

  3. HOW MUCH BLOOD DO WE HAVE? • You have about 10 pints of blood pumping through your body. • Plasma is the liquid portion of blood and it is 55% of the blood volume. • Red blood cells transport oxygen from the lungs and carbon dioxide to the lungs for removal. • Antigens on the surface of the RBC give them their blood characteristics. • White blood cells produce antibodies to disable and/or destroy invaders. • Platelets help to clot blood. The protein fribrin catches red blood cells.

  4. BLOOD TYPING In 1901 Karl Landsteiner discovered the human blood groups. The difference in blood groups are due to the presence or absence of certain protein molecules called antigens and antibodies. Landsteiner broke the groups into the familiar A, B, AB, and O.

  5. BLOOD TYPING Today we use: Besides A, B, AB, and O there are over 100 blood factors that can be used to identify a person. Example: RH factor Until the 1990’s scientists used these factors to identify someone. DNA

  6. BLOOD AT THE CRIME SCENE Hemastix will turn from yellow to dark green if blood is present. Is it blood? We use presumptive tests to answer this question. Hemastix – reacts with the hemoglobin in blood.

  7. BLOOD AT THE CRIME SCENE • Presumptive Tests (continued) • Kastle-Meyer Test • A drop of phenolphthalin reagent is added to the sample, and after a few seconds, a drop of hydrogen peroxide is applied to the swab. If the swab turns pink rapidly, it is said to test presumptive positive for blood.

  8. BLOOD AT THE CRIME SCENE Presumptive Tests (continued) Luminol – reacts with iron present in blood and a chemical reaction that leads to luminescence revealing the location of the blood. Picks up blood even if diluted up to 10,000 times.

  9. BLOOD AT THE CRIME SCENE From what species? Precipitin or Gel Diffusion – Blood from mummies 4,000 – 5,000 years old still give positive results! If it’s human blood, whose is it? • ABO Testing • DNA Fingerprinting

  10. INTERPRETING BLOOD SPATTER • Blood spatter can tell us the following: • Direction blood droplet was moving • Where the blood droplet came from • Type of weapon used in the crime • Position of victim, suspects, and objects • Sequence of events

  11. INTERPRETING BLOOD SPATTER The pointed part of the blood spatter give you the direction the blood was traveling at the point of impact. How to tell the direction that blood droplet was moving. Here is a picture of some blood spatter which hit a surface.

  12. INTERPRETING BLOOD SPATTER • Working with multiple droplets can tell were the victim was located when the crime was committed.

  13. TYPES OF BLOOD SPATTER Irregular spatter pattern indicate higher fall. Passive blood spatter is created by the force of gravity. Height determines diameter of blood spatter.

  14. TYPES OF BLOOD SPATTER • Projected blood spatter occurs when energy has been transferred to the blood source. • Low, Medium & High Velocity • Falling blood drops • Gunshot wounds • Arterial Spurting • Cutting of an artery • Expiratory • Blood from mouth or nose

  15. TYPES OF BLOOD SPATTER • Contact or Transfer blood spatter occurs when an object with blood on it comes into contact with other objects. • Wipe • Swipe

  16. ANGLE OF IMPACT • The angle of impact is useful in determining where blood spatter originated from. • To find the angle of impact: Sin (angle) = Width / Length

  17. Activity OneBlood Typing • In this activity, you will be testing samples of blood to determine the blood type.

  18. Activity Two:Determining the Height of blood spatter • In this activity, you will make passive blood drops from specific heights, than by graphing the diameters of known blood drops, use the graph to determine the height that unknown blood drops.

  19. Activity Three:Blood Spatter Patterns • In this activity, you will be spattering blood on paper and analyzing the patterns.

  20. Activity Four:Angle of impact • In this activity you will be dropping blood at specific angles, calculating the angles that your spatter hit the paper, and then comparing the two.

  21. Activity Five:Determining the Origin • In this activity, you will take the blood spatter sheets you made in activity two and use them to determine their origin.

  22. Now its time to play with Blood

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